Models for sediment yield in mountainous Greek catchments

In this study we explore the controls over suspended sediment yield in 11 stations situated along six major rivers of Western - Northern Greece (Arachthos, Achelooos, Evinos, Aoos, Kalamas and Aliakmon). Values of area specific sediment yield for these stations come from reanalysis of existing records, by adaptation of the broken rating curve concept, and range from 140 to 2300 t km−2 y−1. We investigate the correlations among suspended sediment yield values and many geomorphic - topographic, morphometric, textural, tectonic, geological-lithological and climatic (precipitation-runoff) characteristics of the corresponding basins, along with land cover variables and RUSLE factors (LS, R, K and C RUSLE), from maps of the European Soil Data Center. We find the principal controls to be slope and lithology followed by precipitation, runoff and landslide frequency. Factors such as ground cover (percentage of barren land within the basin) and alluviation of the river, have also some relevance. With the use of stepwise multiple regression analysis we build a model that employs three variables: slope (in percent), precipitation (mean annual, in mm) and lithology (as percentage of the easily erodible geological formations within the catchment), where the contribution of lithology is an additive term to the slope-precipitation power relationship. The proposed model achieves good statistics (NSE = 0.84). From the other models tested with our data set BQART performs well while RUSLE2015 of the ESDC performs poorly.